JP2010518950A - Finger joint prosthesis - Google Patents

Abstract

  A body (14) having first and second articulation elements pivotally interconnected about a pivot axis, the first and second articulation elements comprising proximal phalanges and Anchor members (30, 32) for fixation to the distal phalanx are respectively extended, and eye holes (40, 42) having openings for receiving fixing screws are respectively provided in the anchor members (30, 32). 44), the first joint element comprises an outer hollow body having an insertion opening (22), and the second joint element is an inner hollow body. When the prosthesis is mounted, the inner hollow body can be inserted into the outer hollow body through the insertion opening (22) so as to be rotatable relative to the inner hollow body, and the outer hollow body is disposed inside the inner hollow body. The spindle (48) can be inserted and arranged for relative rotation with the shaft.

Description

  The present invention relates to a finger joint prosthesis provided with a main body portion having first and second joint elements. These joint elements are pivotally interconnected around one pivot axis, and each joint element has an anchor member for fixing to the proximal phalange and / or the distal phalanx. Yes. Each anchor member is also provided with one or more eye holes having openings for receiving fixing screws.

  A dysfunction in the middle joint of a finger can be caused by a genetic disorder, ie, arthropathy, as one cause. In this case, the disease can lead to wear of the articular cartilage, and as a result of the joint surface being completely deformed by the action of a corresponding inappropriate strain and pressure, it can lead to functional limitations due to pain and loss of joint function. In addition, a dysfunction in the middle joint of a finger may occur due to an injury such as a dislocation of a finger joint or a fracture. Initial treatment when a finger joint is fractured generally results in a condition called “traumatic joint sequelae” of the joint, which also induces painful functional limitation and loss of function of the middle joint of the finger.

  One countermeasure for avoiding the above-mentioned problems that cause functional problems is to fix the finger joints at a position suitable for the function. While this method does indeed result in relief from pain, it means that the knuckles are functionally completely unusable.

  In the initial operation of transplanting a finger joint prosthesis, it was necessary to cut the inner lateral ligament in the finger joint for access to the ulna side. In that case, the finger joint is dislocated laterally, and the palm side plate portion is separated. Next, the size of the head of the first phalanx and the base of the second phalange is shaped to ensure a given gap between the phalanges. Then, a rectangular space is drilled along the central axis in each phalanx with a surgical cutting instrument. In this rectangular space, the shaft guide is fixed with a bonding agent. After that, a pair of joint elements are respectively mounted in the shaft guide by the anchor members provided respectively, the phalanges are bent back, and the spindles are inserted by aligning the openings of the anchor members. The first and second joint elements are hingedly connected to each other.

  In the procedure of the transplant operation of the known finger joint prosthesis as described above, the finger joint must be dislocated laterally, so that the extensor tendon system of the finger joint, the two flexor tendons and the lateral ligaments are stimulated, Therefore, the subsequent operability is adversely affected. In addition, since the shaft guide has to be inserted in the direction of the central axis in the finger joint, a large amount of bone tissue is sacrificed for the operation of implanting the finger joint prosthesis.

  A significantly improved finger joint prosthesis is known from EP 1096906 by Christophe Lanft, one of the inventors of the present application. This finger joint prosthesis enables a new surgical technique improved so as to avoid the above-mentioned problems. In the technique disclosed in Patent Document 1, after the finger joint prosthesis is in an assembled state, it can be inserted into a slit previously shaped into a phalanx from the radial direction of the finger and transplanted, This greatly simplifies wearing and minimizes finger damage.

  However, this improved finger joint prosthesis has an extremely sophisticated structure and suffers from insufficient mechanical strength and durability.

European Patent No. 1096906

  Accordingly, it is an object of the present invention to further improve a finger joint prosthesis of the type described at the outset, while at least partially avoiding the above-mentioned problems of large bone tissue loss, while providing a high level of structural stability. And a finger joint prosthesis capable of facilitating transplantation with little damage to the patient.

  In order to achieve the above-mentioned object, a finger joint prosthesis according to an embodiment of the present invention is of the type described at the beginning, wherein the first joint element includes an outer hollow body having an insertion opening, The joint element includes an inner hollow body, and when the prosthesis is mounted, the inner hollow body can be inserted and arranged in the outer hollow body through the insertion opening so as to be rotatable relative to the inner element. A spindle can be inserted into the hollow body so as to be relatively rotatable with the outer hollow body. Each of the outer hollow body and the inner hollow body has an outer peripheral surface and an inner peripheral surface. The outer peripheral surface of the inner hollow body is slightly smaller than the inner peripheral surface of the outer hollow body, so that the inner hollow body can be inserted into the outer hollow body in a relatively rotatable manner in a state where the prosthesis is mounted. The inner peripheral surface of the outer hollow body and the outer peripheral surface of the inner hollow body are both rotationally symmetric and have substantially the same diameter to ensure smooth relative rotation without vibration. As described above, the combination structure of both hollow bodies that can rotate relative to each other so that one of the two hollow bodies slides inside the other is particularly disclosed in Patent Document 1 in which the torsional force is borne exclusively by the central spindle. Is advantageous in that the geometric moment of inertia related to torsion and bending can be greatly improved.

  According to a particularly preferred embodiment of the invention, the outer hollow body and the inner hollow body are both hollow cylindrical.

  Since metal has high stability and fatigue strength when used in vivo, it has been confirmed that it is particularly advantageous that the outer hollow body and the inner hollow body are made of metal. In this respect, titanium has particularly excellent slidability and friction characteristics, and titanium nitride has excellent biocompatibility and extremely good wear characteristics. Therefore, it is particularly preferable to use these metals.

  If the outer and inner hollow bodies are made of metal, the spindle can be made of a plastic material that can be a particularly suitable material for combination with these hollow bodies. It is particularly preferable to use PE (polyethylene). However, the spindle may be made of metal.

  In order to reduce sliding friction between the mutually facing end surfaces of the inner hollow body and the outer hollow body, an annular disk or washer made of plastic material is interposed between the outer end surface of the inner hollow body and the inner end surface of the outer hollow body. This annular disk is also preferably made of PE.

  The finger joint prosthesis according to the present invention can be suitably used for a PIP joint (proximal interphalangeal joint) and can support the force generated in the joint without any problem. In order to obtain the normally required bearing capacity, it is desirable that the outer diameter of the outer hollow body be about 1.5 to 2 times the outer diameter of the spindle. In the case of a PIP joint, the outer hollow body preferably has an outer shape of 12 mm and the spindle has an outer shape of 6 mm. However, it is also within the scope of the present invention to be used as an alternative for a DIP joint (distal interphalangeal joint) or MCP joint (metacarpal interphalangeal joint). In principle, the structure according to the invention can be implemented for various finger joints with an appropriate dimensional design, while maintaining the advantageous dimensional relationships described above.

  Between the outer hollow body and the inner hollow body, an abutting means for limiting the angle range of the relative rotation to a predetermined angle can be provided. In a particularly preferred embodiment, the abutting means comprises a substantially trapezoidal protrusion provided on the outer peripheral surface of the inner hollow body, and the rising end surface of the trapezoidal part is hollow outside when the prosthesis is mounted. It is provided so that it can collide with the edge of the body insertion opening. The angle range of relative rotation is preferably 0 to 135 degrees, and more preferably 0 to 90 degrees.

  In order to achieve the above object, a finger joint prosthesis according to still another embodiment of the present invention is of the type described at the beginning, and each anchor member of the first and second joint elements has at least one leg. -Like branch part. The branch portion preferably extends in a direction parallel to the rotation axis, that is, a direction orthogonal to the longitudinal axis of the anchor member. In this case, it is necessary to shape a concave part for receiving the branch part on the side of the slit for the anchor member in the skin part of the phalanx. At least one leg-shaped branch portion provided on the anchor member is a finger when a load is applied in a direction transverse to the longitudinal direction of the anchor member, that is, in the longitudinal direction of the body portion of the finger joint prosthesis. It functions as a support for supporting the joint prosthesis.

  The anchor member may be provided with a plurality of leg-like branch portions. In this case, the anchor member is provided with one or more cutout portions along the longitudinal axis, and the branch portions are spaced apart by the cutout portions. It is better to arrange them with a gap. When the prosthesis is viewed from directly above, the plurality of branch portions have an almost W-shaped, U-shaped or V-shaped contour of the anchor portion. These branch portions do not hinder the tightening operation of the fixing screw to the phalanx, and at the same time, the fixing screw can be screwed in an inclined direction with respect to the rotation axis. In addition, it is desirable to be provided at a position shifted from the opening of the eye hole portion of the anchor member. In order to ensure such an inclined screwed state, it is also preferable to form a crotch base of a notch between adjacent branch portions of the anchor member on an inclined surface.

  It is preferable that the leg-shaped branch portion is provided on the front surface side of the anchor member, that is, the portion located on the phalanx side in the mounted state.

  For supporting force acting on the anchor member, at least one branch portion is provided at the outer free end far from the pivot axis of the anchor member, and another one branch portion is provided on the anchor member. It has been confirmed that it is particularly advantageous to provide it in the vicinity of the joint with the hollow body.

  By selectively providing an additional branch on the front side of the anchor member, that is, the edge opposite to the phalanx in the mounted state, The contact surface area can be further expanded.

  The branch part on the front surface side of the anchor member and / or the rear surface side opposite to the anchor member gives the anchor member a substantially V-shaped or W-shaped contour when the prosthesis is viewed from directly above, In this case, the relatively longer anchor member on the proximal phalanx side in the mounted state has a W-shaped contour shape, whereas the relatively shorter anchor member on the distal phalanx side in the mounted state. It is desirable that the anchor member has a V-shaped contour shape.

  Further details, features, and advantages of the present invention are described in detail below in conjunction with FIGS. 1-4 illustrating embodiments according to the present invention.

It is a schematic diagram of the middle joint of the finger showing the implantation position of the finger joint prosthesis from the side. It is a side view of the finger joint prosthesis by this invention. It is a top view of the finger joint prosthesis of FIG. FIG. 4 is an exploded perspective view of the finger joint prosthesis of FIG. 3.

  FIG. 1 is a schematic side view of a middle joint 2 of a finger between a proximal (ie, close to the body) phalange 4 and a distal (ie, away from the body) phalange 6. In the figure, the extensor tendon 8 is shown below the biphalanges, and the flexor tendon 10 is shown above the biphalanges.

  The finger joint prosthesis shown in FIGS. 2 to 4 is for transplanting from the side of the finger straightly forward to the inside of the finger joint shown in FIG. The transplant position is the hinge joint site represented by the center circle in FIG.

  FIG. 2 is a side view showing the finger joint prosthesis in an assembled state. The prosthesis includes a main body portion 14 including a first joint element and a second joint element that are connected to each other in a hinge shape. In this case, the second joint element is connected to the first joint element so as to be rotatable around a rotation axis A shown in FIG.

  2 and 3 show a side view and a plan view of the finger joint prosthesis in the implantation position. The first joint element includes an outer hollow cylinder 20 which has an insertion opening 22 on one side of the pivot axis A. The second joint element includes an inner hollow cylinder 24 that is inserted into the insertion opening 22 of the outer hollow cylinder 20 so as to be relatively rotatable. The outer hollow cylinder covers almost half of the outer peripheral surface of the inner hollow cylinder at the peripheral surface excluding the insertion opening. On the outer peripheral surface of the inner hollow cylinder 24 of the second joint element, an abutting end surface on the inner hollow cylinder 24 side for abutting with the edge of the insertion opening 22 of the outer hollow cylinder 20 is formed at about 90 degrees. A substantially trapezoidal abutting protrusion 28 extending over the angular region is formed. The allowable angular range of the relative rotation of the inner hollow cylinder with respect to the outer hollow cylinder can be limited to a desired value by an appropriate dimensional design of the abutting protrusion 28.

  The proximal anchor member 30 that extends toward the body is integrally formed on the outer peripheral surface of the outer hollow cylinder 20 on the side opposite to the insertion opening, thereby constituting a first joint element. Yes. When the direction approaching the phalanx is anterior and the direction away from the phalanx is the rear along the mounting direction toward the phalanx to be transplanted with the knuckles, the proximal anchor member 30 is The outer hollow cylinder 20 located substantially at the center of the finger joint prosthesis extends from the outer peripheral surface near the rear in a direction orthogonal to the rotational axis A. The proximal anchor member 30 has a surface that extends in a direction orthogonal to the rotational axis A of the main body portion 14. The height dimension of the proximal anchor member is about ¼ of the total length of the main body portion 14 along the rotational axis direction. As can be seen from FIG. 2, the proximal anchor member 30 is formed on the outer peripheral surface of the outer hollow cylinder 20 to some extent above the horizontal plane including the rotation axis.

  In the implantation position shown in FIG. 2, the distal anchor member 32, which will extend away from the body, is integrally formed on the inner hollow cylinder 24 from the rear side to the substantially central portion of the abutting projection 28, It extends in the same plane as the proximal anchor member 30. The distal anchor member 32 extends from the inner hollow cylinder 24 in a direction perpendicular to the rotation axis A so as to go away from the body, and is also planar.

  The proximal anchor member 30 and the distal anchor member 32 are integrally provided with leg-like branch portions 34 and 36, respectively, on the front surface side that is the phalanx side when the prosthetic device is mounted. These branch portions 34 and 36 extend forward so as to cross the longitudinal axis direction of the anchor members 30 and 32 within a range extending substantially half the axial length of the main body portion 14. . Here, at least one branching portion 34, 36 is formed at the free end far from the pivot axis of each anchor member 30, 32, thereby applying a load acting on each anchor member 30, 32, respectively. It can be supported even at the free end.

  The distal anchor member 32 is pivotable upward within an angular range of about 90 degrees relative to the proximal anchor member 30 from the illustrated implantation position.

  A first eye hole 42 is integrally formed on the upper surface side of the proximal anchor member 30 at a position slightly inward from the outer free end of the anchor member 30. Further, on the upper surface side of the proximal anchor member 30, the second eye hole part 40 having the same geometric shape is also integrated at a position close to the inside from the first eye hole part toward the outer hollow cylinder 20. Is formed. The first eye hole part 42 and the second eye hole part 40 can be screwed on the proximal anchor member 30 by inserting a fixing screw into the opening of these eye hole parts and screwing the anchor member to the phalanx. Therefore, it is disposed so as to be accurately positioned in the region of the notch formed between the leg-like branch portions 34 extending substantially parallel to the rotation axis A of the main body portion 14. ing. A cut between the branch portions 34 of the proximal anchor member 30 so that the fixing screw can be screwed into the phalanx through the opening of the eye hole portions 42 and 40 in a direction inclined with respect to the rotation axis A. An inclined surface 38 is formed in the crotch portion of the notch portion adjacent to the eye hole portions 42 and 40. That is, on this inclined surface, the material thickness gradually increases from the front side toward the rear side to the total thickness of the anchor member of 0.7 to 1.3 mm. The eye holes 42 and 40 may be inclined about 5 to 10 degrees from the vertical surface for the purpose of assisting the fixing screw to be inclined.

  The proximal anchor member 30 shown has a substantially W-shaped profile when viewed from directly above.

  The rear side of the proximal anchor member 30 (the side facing away from the phalanx in the implantation position) is rearward from the rear end of the outer hollow cylinder 20 with an angular gradient of about 45 degrees with respect to the rotational axis A. It extends to the protruding apex, and further reaches the outer free end with a reverse gradient at an angle shallower than 45 degrees from the apex. The same applies to the distal anchor member, and the protrusions of the anchor members 30 and 32 formed in this manner adapt the anchor members to the original shape of the phalanx, thereby improving the mobility of the artificial finger joint. In order to improve the mechanical stability by increasing the contact support surface in the phalange without hindrance, the apex formed at the discharge apex between the backward gradient and the reverse gradient The angle is obtuse, preferably in the range of 150 to 170 degrees.

  The distal anchor member 32 is also provided with two branch portions 36 extending substantially parallel to the rotation axis A. These branch portions 36 are spaced from each other by a notch portion having an inclined surface at the crotch portion on the lower surface side. On the lower surface side of the distal anchor member 32, a third eye hole portion 44 is provided so as to protrude downward at a position slightly shifted outward (distal side) from the notch portion. The third eye hole 44 is formed integrally with the top of the distal end edge of the distal anchor member 32 in the distal direction.

  A PE spindle 48 is formed on one end surface of the outer hollow cylinder 20 in order to connect the first joint element and the second joint element configured as described above in a hinge-like manner so as to be relatively rotatable. It is inserted from the opening. The spindle 48 passes through the cylindrical inner space of the inner hollow cylinder 24 and fixes the inner hollow cylinder 24 in the outer hollow cylinder 20. The spindle 48 is engaged with the outer hollow cylinder 20 by an appropriate press fit between the spindle 48 and the outer hollow cylinder 20. A reduced-diameter engaging portion that can be pushed into the front end surface of the outer hollow cylinder 20 is provided at the tip of the spindle 48.

  The outer end face of the inner hollow cylinder 24 is made of titanium nitride, and the inner end face of the outer hollow cylinder 20 is also made of titanium nitride. In order to reduce sliding friction between these end faces, an annular disk 50 made of PE is interposed between both end faces. Has been.

  In order to transplant this finger joint prosthesis to the finger joint, after the lateral ligament of the finger joint part is cut off, a rotary milling is performed from one side of the longitudinal axis of the phalanx to the part indicated by the center circle in FIG. A cylindrical hole is drilled sideways by cutting surgery. The central axis of this cutting hole coincides with the rotational axis of the two phalanges 4 and 6 at the pivotal start point at which the distal phalange 6 transitions from a state of extending straight forward to a state of bending downward. The inner diameter and length of the cutting hole correspond to the outer diameter and length of the body portion 14 of the artificial joint. After forming a laterally cut hole, two slits 52 and 54 extending from the cut hole to each phalanx in the longitudinal direction are similarly formed by a cutting operation from one side surface of the phalange. Needless to say, the contour shape of the slits 52 and 54 matches the outer shape of the anchor members 30 and 32.

  After drilling the cutting holes and slits 52, 54, the finger joint prosthesis is inserted into the horizontal cutting hole from its front end, and the eye holes 40, 42, 44 are brought into contact with the phalanges by the same horizontal pushing operation. Both anchor members 30, 32 are pushed into the slits 52, 54 until they come into contact. These anchor members 30 and 32 are securely fixed to the corresponding phalanges 4 and 6 by passing titanium fixing screws through the openings of the eye holes 40, 42 and 44 and screwing them into the phalange tissue. .

  Each component of the finger joint prosthesis is preferably made of metal, and particularly preferably made of titanium or titanium nitride. These materials are advantageous in that they have a porous surface, and the growth of bone tissue within the porous surface tissue ensures a durable and high level of implantation stability. Furthermore, it is possible to provide a coating layer having biocompatibility that promotes the growth of bone tissue on the surface of the material. For example, hydroxyapatite is particularly excellent for this purpose.

  In order to obtain good friction resistance between the spindle and the inner hollow cylinder, not only the spindle and inner hollow body are both made of wear-resistant material, but also the spindle and inner hollow cylinder have slightly different hardness. It is desirable to be made of a material. If a hollow body made of titanium or titanium nitride is used for the inner hollow cylinder, the spindle is advantageously made of a wear-resistant plastic material, in particular ultra high molecular weight polyethylene (UHMWPE). However, in addition to this, it is possible to employ any combination of optimum materials having good low friction characteristics.

  In accordance with the size of the finger joint to be replaced with the prosthesis, the size of the finger joint prosthesis according to the present invention is preferably within the following range.

-Outer diameter of finger joint prosthesis body: 6-8 mm
・ Outer diameter of spindle: 3-4mm
-Length of anchor member: 4 to 8 mm
-Thickness of anchor member: 0.7 to 1.3 mm

  The above embodiment describes the case where the middle joint of the finger is replaced by the finger joint prosthesis according to the present invention. Similarly, the finger joint prosthesis according to the present invention can be used to replace the tip joint of a finger by appropriately adapting the outer shape while maintaining the relative relationship of dimensions.

  The technical feature requirement of the present invention includes not only the feature requirement according to each claim but also a combination of individual claims. Each feature disclosed in the present specification (including abstract) and its details, particularly the three-dimensional shape shown in the drawings, are claimed as essential requirements of the present invention as long as they are novel over the prior art individually or in combination. As described in the range.

A pivot axis 2 middle joint 4 of the finger 4 proximal phalanx 6 distal phalange 8 extensor tendon 10 flexor tendon 14 body 20 outer hollow cylinder 22 insertion opening 24 inner hollow cylinder 28 abutting means 30 near Position anchor member 32 Distal anchor member 34 Branch portion 36 Branch portion 38 Inclined surface 40 First eye hole portion 42 Second eye hole portion 44 Third eye hole portion 46 End face opening 48 of outer hollow cylinder Spindle 50 Annular disk 52 Slit 54 Slit

Claims (15)

A body portion (14) having first and second articulation elements pivotally interconnected about one pivot axis, the first and second articulation elements comprising proximal phalanges and Anchor members (30, 32) for fixation to the distal phalanx are respectively extended, and eye holes (40, 42) having openings for receiving fixing screws are provided in these anchor members (30, 32). , 44) are provided,
The first joint element comprises an outer hollow body having an insertion opening (22);
The second joint element comprises an inner hollow body;
In the prosthesis mounting state, the inner hollow body can be inserted and arranged in the outer hollow body through the insertion opening (22) so as to be relatively rotatable, and the outer hollow body is inserted into the inner hollow body. A finger joint prosthesis characterized in that a spindle (48) can be inserted and arranged for relative rotation with a hollow body. The finger joint prosthesis according to claim 1, wherein the outer hollow body and the inner hollow body are made of metal. The finger joint prosthesis according to claim 1 or 2, wherein the spindle is made of a plastic material. 4. An annular disk (50) is interposed between the inner end surface of the outer hollow body and the outer end surface of the inner hollow body facing the inner end surface. The finger joint prosthesis according to item 1. 5. The finger joint prosthesis according to claim 1, wherein an outer diameter of the outer hollow body is 1.5 to 2 times an outer diameter of the spindle. The finger joint prosthesis according to any one of claims 1 to 5, wherein the outer hollow body and the inner hollow body are both cylindrical. The finger joint prosthesis according to any one of claims 1 to 6, wherein an abutting means (28) is provided between the outer hollow body and the inner hollow body. The finger joint prosthesis according to claim 7, wherein the abutting means (28) includes a protrusion provided on an outer peripheral surface of the inner hollow body. The finger joint prosthesis according to claim 7 or 8, characterized in that the abutting means (28) comprises a protrusion over an angle range of 130 degrees. A body portion (14) having first and second articulation elements pivotally interconnected about one pivot axis, the first and second articulation elements comprising proximal phalanges and Anchor members (30, 32) for fixation to the distal phalanx are respectively extended, and eye holes (40, 42) having openings for receiving fixing screws are provided in these anchor members (30, 32). , 44) are provided,
The finger joint prosthesis characterized in that the anchor member (30, 32) includes at least one branch portion (34, 36) extending in parallel with the rotational axis. The finger joint prosthesis according to claim 10, wherein the branch portion is provided at a free end of the anchor member that is farther from the rotation axis. The anchor member (30, 32) has a plurality of branches (34, 36), and these branches are formed by one or more notches along the longitudinal axis of the anchor member (30, 32). The finger joint prosthesis according to claim 10 or 11, wherein the finger joint prosthesis is arranged at intervals. The finger joint prosthesis according to any one of claims 10 to 12, wherein at least one of the branch parts (34, 36) is provided on a front side of the anchor member (30, 32). Ingredients. The finger joint prosthesis according to any one of claims 10 to 13, wherein an additional branch portion is further provided on the rear surface side of the anchor member (30, 32). The finger joint prosthesis according to claim 14, wherein the branch portion on the rear surface side is formed according to the shape of the phalanx.

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